// 云函数入口文件
const cloud = require('wx-server-sdk')

cloud.init({ env: cloud.DYNAMIC_CURRENT_ENV }) // 使用当前云环境

const db = cloud.database()
const _ = db.command
const $ = _.aggregate

// 云函数入口函数
exports.main = async (event, context) => {
  id = event.Novelid
  return await db.collection('bookDetails')
    .aggregate()
    .lookup({
      from: 'bookClassify',
      localField: 'bookClassify',
      foreignField: '_id',
      as: 'class',
    })
    .match({_id : id})
    .replaceRoot({
      newRoot: $.mergeObjects([$.arrayElemAt(['$class', 0]), '$$ROOT'])
    })
    .end()
}